Adjustable plumb bob



May l0, 1949. sUvERKROP ADJUSTABLE PLUMB BOB v Filed July 5o, 1945 m o y# 4 n, Nwgwmwy//l @SWW Patented May 10, l949 UNITED STATES `PATENT GFFICE ADJUSTABLE PLUMB BOB Lew Suverkrop, Bakersfield, Calif.

Application July 30, 1945,A Serial'No. 607,877

6 Claims. l

My invention relates particularly to the geometrical instrument known asthe plumb bob used tof establish a location vertically above orY below a. point. The improvements apply especially to the types used by builders, surveyors, etc. in the morel exacting Work requiring line adjustment of the string length so as to place the plumb bob point closely above a reference point. For such work, the ordinary plumb bob, having noprovision for holding or' adjusting the string', 'has serious disadvantages. To adjust the length of the string', it mustbe knotted or otherwise manipulated, or a separate attachment must be employedfor thepurpose. I-fy the adjustment ismade with sufficient precision, it is usually a time consuming job. The lack of a place provided for carrying-the string when the plumb bob is not'in usezis an additionall disadvantage. The string is usually Wound aboutI the neck of the bob or looped in figure-eight fashion over its body; but this is. untidy, the string frequently becomes tangled, and time is consumed in winding or With-A drawing the string.

Plumb bobs have. beeny constructed heretofore With reels, usually with the common. advantage over the ordinary type ofbob in that they provide a place for the string so it willfnot become tangled when the bob is not in use. Those bobs are of two types. The reels are either internal or eX- ternal. In general, the internal reel type permits lne adjustment of the string length; but. has the disadvantages of somewhat complicated and delicate mechanism, and is slow in operationespecially in Winding up the string. In the external type, the string may be quickly wound up; but-such bobs have the disadvantage of not permitting quick, fine adjustment of the string length. Moreover, this type of plumb bob requires a string hook andl this is usually made integral wit/haa larger'part of.' the bob all of which must beA replaced in event of damage to the hook. In addition, the hook is difli'cultto manipulate.

Onel object-3 ofv this invention is toy provide a plumbbobA with a; reel on which: the string may bemore quickly Wound than in the internal reel type, and; fromwhich the string-i may be more quicklyl withdrawn than isithev usual external. reel type. A-. further' object is to'provide a plumb bobl withta reelwhich may be directly rotated by the hand forthe purpose ofY adjusting string length; A further object is to provide a plumb bob with a headA affording a string hook which will1facili'- tate: the.. introduction offl the string into position for. suspensiono the plumb-bob; A further object is to-provide a detachable head andstrirrg-.v head'l 2 for a plumb bob so that the head may be readily replacedin event of damage, without replacing any other par-t oiv the fplumb bob. A further object is to provide a detachable plumb bob head with a through hole so that the plumb bob may be used as an ordinary plumb bob in the event of damagev to the head, until such timeas it may be conven ient tofreplace the head A further object'is to.` provide a plumb bob with an external rotatable` reel on which the string may be wound and: from. whichV the string may be Withdrawn, with fric= tion control of the reels rotation sothat the reeli will stand and hold any amount of string payed outfrom: it against any action due to the Weighty of the bob. A further object of the inventionis to provide that friction with anadjustment. so.` that the degreeof control of the reels rotatiorr maybe regulated as desired; A further object isFl to provide that friction control with a self-con-x tained spring which will automaticallyl compen sate for slight dimensional changes due to wear or weathern conditions so as tomaintain a sub;= stantially constant friction. These and other objects ofthe invention will be clear from the fol.- lowing description and the accompanying illus.- trations, in which:

Fig. 1 isa cross section, taken along theliney A. invFig. 3, showing a plumb bob madeaocordin'g; to.I this specication.

Fig. 2 is an elevation of the same;

Fig. 3 is a plan of the same.

Figs; 4 and 5 are elevations of a head for plumb'. bobs madeaccording to this specification.

Fig. 6i is a cross section4 of a detail of another embodiment of' plumb bob made according to this. specication.

Thel plumb bob shown iny Fig. 1 consists of' a body 50 I of the usual form and materialand fitted with the usual hardened point or indicatorL 502; The upper end or neck ofthe bodyr 50| is of cylin drical form to receive the rotatable reel 503 and' isrecessed for the friction washer 504 which is preferably keyed against rotation by the pin 505-- inthe body 501. The upper termination ofl the neck of the body 50|? is threaded to receive ai threadedshank on the head 506.

The string reel 503 is preferably provided with a countersunk hole 501i for holding one end' ofthe string to the reely 503. Except for the action ofy the friction Washer 504, the string reel 503 is free to rotate on the neck of the plumb bob body 5&1. The upper ange of the string reel 50'3 is'v preferably Wide enough to provide a suitablel knurled surface for gripping with the fingers and so as to. carrythe countersunk hole 501. `The`4` reel may be made of one piece as shown or can be constructed of two flanges permanently attached te the ends of a short piece of tubing. The lower Flange may be made rather thin and should t into the recess at the top of the plumb bob body 55H as shown.

The friction washer or aperture disc 504 may be made of nbre or phenolic condensation product er like material. By placing a raised ring at the outer edge of the washer on one side and another raised ring at the inner edge of the washer on the other side, as illustrated in Figs. 1 and 6, these rings bear against the reel and body respectively, and the thin part of the washer between these rings serves as a spring. This spring compensates for any irregularities in the surfaces of these parts which are in contact with the friction washer 504, and for any changes in dimensions due to temperature or weather conditions, thereby maintaining a substantially constant friction.

The threaded shank of the head 506 is split with a saw slot 508 as Shown in Figs. 4 and 5 so that the threads fit snug in the threaded hole in the body 50 l. A capstan hole 509 is provided for turning the head 506 by means of a common adjusting pin or small nail. In this way the distance between the shoulder of the head 506 and the friction washer 504 may be adjusted so as to vary the friction of the washer 504 against the reel 503. The snug iit of the head 505 in the body -l 55E prevents accidental rotation of the head 505 so that the adjustment is retained.

The so-called hook part of the head 506 is formed by the intersection of two slots, 5I0 and 5l l, shown in the various illustrations, which are 'i milled in the metal of which the head is made. One of these, 550, is vertical and extends outward from the axis of the head. The other slot, 5I l, slopes upward slightly as it extends outward from the center of the head. The plane of the slot 5l l slopes so that it intersects slot 5|!! in a line that tilts slightly upward from a perpendicular eX- tending outward from the axis of the head, and the plane of the slot 5H also slopes slightly upward from a perpendicular to the plane of slot 525. The intersection of such planes 5l0 and 5H results in a rather sharp edge which will cut the plumb bob string unless rounded as at 5I 2 in Fig. 4:. In effect, the intersecting slots 5l0 and 5H denne a notch into which projects a tongue terminating in rounded edge 5|2, the sides of said tongue being parallel to the side surfaces defining said notch. A flange 5l 3 is formed on the head to shoulder against the reel 503 and the upper part of the head 506 is preferably roughly liemispherical in form as indicated in the drawings and at 5M in Fig. 5. From Figs. l, 2 and 6, it will be seen that flange 5l5 has a smaller diameter than the upper iiange of reel 503. Between the hemispherical knob 5|4 and the flange 5l3 is a slight recess 524 which is annular. The slot 5H intersects the upper part of the recess 525 as shown in Figs. 2, 3, and 5; and the intersection, which otherwise would form a sharp corner that would Wear the string, is rounded oi at 5l5 as indicated in Figs. 3 and 5. As the string passes from the reel, around at least a portion of annular recess 524, into slot 5l I, and up through slot 5l0, said string passes around the root portion of the tongue which terminates in end 5l2. `Said portion of recess 524 and the root portion of said tongue provide adjoining snubbing surfaces dening a somewhat tortucus path and their function regarding the string is very similar to that of a snubbing post. Said snubbing function supplements the friction of washer 504 in arresting rotation of reel 553 and maintaining any selected position of said reel relative to the body 5M. A hole 5l6 runs through the body of the head 555 in Fig. 3 and 5l8 in Fig. 6 and may be used for suspending the bob as an ordinary plumb bob without making use of the projection 5l2. This hole 5l6 is drilled precisely central with the plumb bob and when suspended the string bears against the wall of this hole. The slot 5H) is milled to the center of the hole 5i5 but not beyond so that sufcient of the hole 5 l 6 remains for support of the string as described. The intersection between slot 5i i and hole 5|6 is rounded as at 5H in Figs. 1 and 6 to reduce wear on the string. it will thus be seen that in addition to the string snubbing function described above, the inner end of vertical slot 5&0 as deiined by hole 5l aifordsran accurate and readily accessible means for positioning the string in the center of the head 505, whereby the bob is suspended in an accurate, vertical position.

The friction washer key 505 is simply a pin forced into a hole drilled in the body of the plumb This key 555 protrudes from the recess in the body 50i sufficiently to engage a notch or keyway in the friction Washer 554 as indicated in Fig. l. Keying the friction washer 504 in this way makes it more positive in action but is not absolutely necessary and the key 505 may be omitted as indicated in Fig. 6.

Putting the hole in the neck of the body 50| to receive the hook 505 as indicated in Fig. 1 ren duces the cross sectional area and tends to weaken the neck of the body 50i. This may be corrected by having the head constructed as shown in Fig. 6. Here the body or shank of the head 5i8 is sufficiently large to provide the aXle on which the reel 503 rotates and suiiciently long to extend downward directly into the body 50| of the plumb bob. Thus the head 5 l 0 itself is made to serve as an equivalent of the neck of the body 50| with no reduction in cross section other than that of the hole 5l6. As shown in Fig. 6, no adjustment of the friction is provided other than the automatic adjustment due to the flexibility of the friction washer 504. AS shown, the head 5I8 is provided with a taper 559 which is drawn into a suitable seat in the body 50i of the bob by means of the thread 525. However, this taper 5l9 may be omitted and the head 518 screwed adjustably into the body 50! so as to vary the friction of the washer 554 employing the principles of the construction shown in Fig. 1.

For use, the plumb bob string is passed through the hole 501 from above so that a knot on one end of the string is drawn into the countersink of the hole 501. Then the other, free end of the string is formed into a bowline or other permanent loop by means of which the string may be attached to a hook or the like for use.

To prepare the bob for carrying, the body 50i is held in the left hand and, using the right hand,

f the string is wound around the core of the reel 503 until but a couple of inchesof unwound string remain. This remainder is drawn around the hook 5I2, Fig. 4, by passing the string rst into slot 5l l and then into slot 5|0 and drawing it upward against the rounded place 5H, Fig. 1, at the root of the projection 52. The reel 503 is then rotated with the nngers to draw the string around the rounded place 5 l 5, Fig. 5, and into the recess 524. This pulls the loop on the string down to the top of the head 505 and will keep the string 5., ready; for. use without danger. of unintentional looseningor becomingtangled.

To use;r the plumb. bob, the reel 5,03 isfirstro.- tated slightly inthe reverse, direction so as to rel'easeithe; looped end. of the stringfromr thetop of the head 506., Thebody titl is then heldin the left handiand, holding. the looped end of thestring withl theright hand, the string, is pulled. so as to rotate the reel 5,93. and unwind.v a slight excess of string beyond that necessary to suspend the plumb bob in the position wanted. The loop is attached to the desired object andthe string near the plumb bob is passed around the projection l2 as previously described. Then the reel 503 is rotated with the fingers in the direction which will draw the string around the recess 524, thus shortening the string issuing from the bob until the point or indicating means 562 is brought to precisely the height desired. The hooking of the string and the final, minute adjustment of the string may be performed with one hand. In general, passing the string from the reel, around at least part of annular recess 524, into slot 5H, around projection 5l2, and into slot Elli, resernbles passing a string around a snubbing post and then around a projection which serves as a sort of hook for suspending the snubbing post from the string.

Some of the details disclosed in this specification are applicable to and may be used in other devices, and may be used in entirely different arts. Moreover, while I have illustrated and described preferred forms of construction, I do not wish to limit myself to the precise details of structure shown in the drawings, but desire to avail myself of such variations and modifications as come within the scope of the appended claims.

What I claim is:

1. A plumb bob comprising in combination, a body having a central axis arranged to be suspended during use in a vertical position, a flanged reel mounted on the upper end of said body for rotation around said central axis of said body, and a head mounted above the upper flange of said reel and disposed inward from the periphery of said upper flange, said head including slot means constructed and arranged freely to receive a string from the periphery of the upper flange of said reel and dispose said string in a tortuous path to restrain movement thereof relative to said head and also position said string so that it extends upward from said head in alignment with the vertical axis of said body, whereby the upper ange of said reel may readily be manually engaged to rotate the reel in opposite directions to raise or lower said plumb bob when suspended from said string.

2. A plumb bob comprising in combination, a body having a central axis arranged to be Suspended during use in a vertical position, a flanged reel mounted on the upper end of said body for rotation relative thereto around said axis, and a head mounted above said reel and disposed inward from the periphery of the upper flange of said reel, said head including a substantially horizontal annular groove comprising snubbing means and also an open-sided slot shaped to provide a tortuous path for and freely receive a string from said reel, the walls of said slot and said snubbing means co-acting to retard movement of said string relative to said head and also dispose said string so that during use it extends upward from said head in alignment with the vertical axis of said body.

3. A plumb bob comprising in combination, a

body havingr a central axis;I arranged td besuse pended during use in a vertical positioma flanged reel mounted., on, thev upper end of said body for rotation around said central axis of said body, a head mounted above the upper flange of said reel. and! extending. inward from. the periphery of said upper flange, said head being threadably4 connected to said body so as to afford relative adjustment'betweensaid headf and body and said head alsoincluding slot meansv constructed. and arranged freely to receive astring fromy theperiphery of the upper flange of said reel and dispose said string so that it extends upward from said head in alignment with the vertical axis of said body, and disc-like friction means acting between said body and reel to retard relative rotation therebetween, the frictional force exerted by said friction means being variable upon rotation of said head relative to said body.

4. A plumb bob comprising in combination, a body having a central axis arranged to be suspended during use in a vertical position, a flanged reel mounted on the upper end of said body for rotation around said central axis of said body, a head mounted above the upper flange of said reel and extending inward from the periphery of said upper flange, said head having a split stem threadedly connected to and exerting frictional force relative to said body so as to yieldably maintain relative adjustment between said head and body and said head also including slot means constructed and arranged tto receive a string from the periphery of the upper flange of said reel and dispose said string so that it extends upward from said head in alignment with the vertical axis of said body, and disc-like friction means disposed between said body and reel to retard relative rotation therebetween, the frictional force exerted by said friction means being variable upon rota- 4() tion of said head relative to said body.

5. A plumb bob comprising in combination, a body having a central axis arranged to be suspended during use in a vertical position, a flanged reel mounted on the upper end of said body for rotation around said central axis of said body, a head mounted above and in engagement'I with the upper flange of said reel and having a split stem threadably connected to and exerting frictional force relative to said body so as to yieldably maintain relative adjustment between said head and body and said head also including a passageway constructed and arranged to receive a string from the periphery of the upper flange of said reel and dispose said string so that it extends upward from said head in alignment with the vertical axis of said body, and a friction element between said reel and body and acting upon said reel to retard rotation thereof relative to said body.

6. A plumb bob comprising in combination, a body having a central axis arranged to be suspended during use in a vertical position, a flanged reel mounted on the upper end of said body for rotation around said central axis of said body, a head mounted above the upper flange of said reel and disposed inward from the periphery thereof, said head including a passageway constructed and arranged to receive a string from the periphery of said upper flange of said reel and dispose said string so that it extends upward from said head in alignment with the vertical axis of said body, whereby the upper flange of said reel may be manually engaged to rotate said reel in opposite directions to raise or lower said plumb bob when suspended from said string, and friction The following references are of record in the LEW SUVERKROP.

REFERENCES CITED le of this patent:

Number UNITED STATES PATENTS Name Date Garner May 21, 1912 Number 8 Name Date Lewis et a1 Apr. 8, 1913 Ppher May 6, 1913 Windham July 29, 1924 Powell Apr. 9, 1929 Morris July 14, 1931 Spaeth et al Sept. 6, 1932 ONeil Dec. 7, 1937 Julien Feb. 24, 1942 

